1. Field of the Invention
This invention relates to a blade of a blower fan used in cooling car engines and the like.
2. Description of the Prior Art
A conventional blade 12 of a blower fan as shown in FIGS. 5 and 6 projects from the outer periphery of a boss body 11, which has a bimetal 15 secured to a discharge-side surface 13 thereof. In response to a temperature rise of flowing air, the bimetal 15 deforms to increase the amount of camber C of the blade 12, so that the flow rate of the flowing air increases in a high-temperature state. On the other hand, in a low-temperature state, the amount of camber C decreases, so that the flow rate of the flowing air decreases; as a result, the noise of and drive power for the fan decrease.
In the foregoing conventional blade, however, the deformation of the blade 12 following the torsional deformation of the bimetal 15 caused by a temperature rise of the flowing air leads mainly to a variation in the amount of camber C as shown in FIG. 7, not causing a variation in the angle of incidence .alpha. effectively; accordingly, an increase only in the amount of camber C results in no appreciable variation in the flow rate, thus, a desired effect cannot be attained. Therefore, a fan clutch of the temperature-sensitive type must be used inevitably, this complicating a control mechanism, enlarging the whole size of the blower, and increasing the weight thereof.